Study (Year)	Reference	Country	Study Design	Exposure	Timing of Exposure	Outcome 1	Timing of Outcome	Sample Size 2	High Quality 3
Barbone et al. (2019)	[61]	Italy, Slovenia, Croatia, Greece	Prospective	Hair Whole blood Umbilical cord	20 weeks—delivery 20 weeks—delivery At delivery	Bayley-III	18 months	628–1086	Yes
Boucher et al. (2014)	[55]	Canada	Prospective	Umbilical cord	At delivery	FTII, A-not-B test, BSID-II	6.5, 11 months	94	Yes
Castriotta et al. (2020)	[62]	Italy	Prospective	Umbilical cord	20–32 weeks gestation	Bayley-III cognitive	40 months	323	No
Daniels et al. (2004)	[74]	United Kingdom	Prospective	Umbilical cord	At delivery	MCDI, DDST	15, 18 months	1054	Yes
Davidson et al. (2008)	[50]	Republic of Seychelles	Prospective	Hair	At delivery	BSID-II	9, 30 months	225–228	No
Freire et al. (2018)	[68]	Spain	Prospective	Placenta	At delivery	MSCA	48-60 months	302	No
Golding et al. (2016)	[76]	United Kingdom	Prospective	Whole blood	11 weeks gestation	Modified DDST	6, 18, 30, 42 months	2394–2721	No
Hu et al. (2016)	[73]	China	Prospective	Whole blood Umbilical cord	At delivery	GDS	12 months	410	Yes
Jedrychowski et al. (2007)	[56]	Poland	Prospective	Umbilical cord	At delivery	BSID-II	12, 24, 36 months	270–374	No
Kim S et al. (2008)	[57]	South Korea	Prospective	Whole blood Umbilical cord	At delivery	BSID-II, SMS	13-24 months	49–118	No
Kim Y et al. (2018)	[48]	South Korea	Prospective	Whole blood Whole blood Umbilical cord	12–20 weeks gestation 28–42 weeks gestation At delivery	BSID-II	6, 12, 24, 36 months	414–790	Yes
Lederman et al. (2008)	[58]	USA	Prospective	Umbilical cord	At delivery	BSID-II, WPPSI-R	12, 24, 36, 48 months	107-132	No
Lin et al. (2013)		Taiwan	Prospective	Umbilical cord	At delivery	CDIIT	24 months	230	No
Llop et al. (2012)	[59]	Spain	Prospective	Umbilical cord	At delivery	BSID-II	14 months	1683	Yes
Marques et al. (2009)	[45]	Brazil	Prospective	Hair	At delivery	GDS	6, 36, 60 months	82	No
Nisevic et al. (2019)	[63]	Croatia, Italy	Prospective	Umbilical cord	At delivery	Bayley-III	18 months	257	Yes
Nyanza et al. (2020)	[46]	Tanzania	Prospective	Whole blood	16–27 weeks gestation	MDAT	6–12 months	429	No
Oken et al. (2005)	[70]	USA	Prospective	Hair	At delivery	VRM	6 months	135	No
Oken et al. (2008)	[69]	USA	Prospective	Erythrocyte	2nd trimester	PPVT, WRAVMA	36 months	341	Yes
Polanska et al. (2013)	[49]	Poland	Prospective	Hair	30–34 weeks gestation	Bayley-III	12–24 months	303	No
Prpic et al. (2017)	[72]	Croatia	Prospective	Umbilical cord	At delivery	Bayley-III	18 months	135	Yes
Rothenberg et al. (2016)	[44]	China	Prospective	Whole blood Hair	At delivery	BSID-II	12 months	270	Yes
Shah-Kulkarni et al. (2020)	[53]	South Korea	Prospective	Whole blood Whole blood Umbilical cord	12–20 weeks gestation > 28 weeks gestation At delivery	K-BSID-II	6 months	321-467	No
SnojTratnik et al. (2017)	[64]	Slovenia, Croatia	Prospective	Hair Umbilical cord	34 weeks gestation/at delivery At delivery	Bayley-III	16–20 months	280–357	No
Strain et al. (2015)	[54]	Republic of Seychelles	Prospective	Hair	At delivery	BSID-II, CDI	20 months	1241–1265	No
Suzuki et al. (2010)	[43]	Japan	Prospective	Hair	At delivery	NBAS	3 days	498	Yes
Tatsuta et al. (2014)	[67]	Japan	Prospective	Umbilical cord	At delivery	K-ABC	42 months	287	No
Tatsuta et al. (2017)	[71]	Japan	Prospective	Umbilical cord	At delivery	BSID-II, KSPD	18 months	566	Yes
Valent et al. (2013)	[65]	Italy	Prospective	Hair Umbilical cord	20–22 weeks gestationAt delivery	Bayley-III	18 months	271–505	Yes
Wang et al. (2019)	[66]	China	Prospective	Umbilical cord	At delivery	NBNA Bayley-III	3 days18 months	172–265	No
Wu et al. (2014)	[75]	China	Prospective	Umbilical cord	At delivery	NBNA	3 days	418	No
Xu et al. (2016)	[47]	USA	Prospective	Whole blood Umbilical cord	16 weeks—delivery At delivery	NNNS	5 weeks	344	Yes

¹ For explanation of abbreviations, see Table 2. ² Size of primary analysis, or a range if there were multiple primary analyses. ³ 12 or more quality assessment criteria met, including adjustment for key confounders.